plug problems

Hello,
I got a 76 kz900ltd 2nd year now. Carbs were starting to leak, had a friend of a friend rebuild and clean. payed alot.Away my problem now is all 4 plugs carbon up after a short time riding, then runs like @#!%. Was told to run the next plug hotter one. Is this the way to go or is my problem some thing else. New to riding and don"t know anything about motors. Thanks for any help.Pat

Before further addressing carbs, would first assure compression and valve clearances to specs. And also assure good battery being properly charged. Also good fat plug spark, correct ignition timing, and operational advancer unit. In short, all other components should be up to specs before moving to the carbs.

With everything else okay, would first check the pilot air screw adjustments (turn out to go leaner as this allows more air into the mixture) and then check the service float bowl fuel level via the quick easy no-disassembly-required clear plastic tube test. One possible cause for excessively rich mixture is too high float levels.

Maybe the air passages were not adequately cleared.

What is condition of air filter? Any blockage (such as a shop rag left under the seat covering the airbox intake)?

Sometimes pilot jets are damaged during cleaning.

IMO changing to a hotter plug is ill-advised. Should continue the standard NGKB8ES.

Good Luck!

Thanks for your reply.Not realy sure how to do alot of the stuff your said. Talk to rep from ngk and they told me to go to the b7es's. The filter is new and no ragges. I am running a 4into1 kerker header. After running about 10 miles after putting theses new plugs in I checked them and only 1 was carboned up. I am now turning air screw out at small amounts.I am thankful to you and anyone else that helps as I am a virgin when it comes to this stuff. Thank you and everyone for your time answering any questions that I may post.

Would recommend getting a repair manual for information on routine maintenance items such as ignition timing, valve clearance, etc. (most of which is fairly simple and straight forward) as this usually enhances enjoyment of ownership and greatly reduces frustration and expense in keeping these older bikes up to specs.